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/*
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 *
 * Copyright (c) 2000 World Wide Web Consortium,
 * (Massachusetts Institute of Technology, Institut National de
 * Recherche en Informatique et en Automatique, Keio University). All
 * Rights Reserved. This program is distributed under the W3C's Software
 * Intellectual Property License. This program is distributed in the
 * hope that it will be useful, but WITHOUT ANY WARRANTY; without even
 * the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR
 * PURPOSE.
 * See W3C License http://www.w3.org/Consortium/Legal/ for more details.
 */

package org.w3c.dom.events;

/**
 * The <code>EventTarget</code> interface is implemented by all <code>Nodes</code> in an
 * implementation which supports the DOM Event Model. Therefore, this interface can be obtained by
 * using binding-specific casting methods on an instance of the <code>Node</code> interface. The
 * interface allows registration and removal of <code>EventListeners</code> on an
 * <code>EventTarget</code> and dispatch of events to that <code>EventTarget</code>. <p>See also the
 * <a href='http://www.w3.org/TR/2000/REC-DOM-Level-2-Events-20001113'>Document Object Model (DOM)
 * Level 2 Events Specification</a>.
 *
 * @since DOM Level 2
 */
public interface EventTarget {

  /**
   * This method allows the registration of event listeners on the event
   * target. If an <code>EventListener</code> is added to an
   * <code>EventTarget</code> while it is processing an event, it will not
   * be triggered by the current actions but may be triggered during a
   * later stage of event flow, such as the bubbling phase.
   * <br> If multiple identical <code>EventListener</code>s are registered
   * on the same <code>EventTarget</code> with the same parameters the
   * duplicate instances are discarded. They do not cause the
   * <code>EventListener</code> to be called twice and since they are
   * discarded they do not need to be removed with the
   * <code>removeEventListener</code> method.
   *
   * @param type The event type for which the user is registering
   * @param listener The <code>listener</code> parameter takes an interface implemented by the user
   * which contains the methods to be called when the event occurs.
   * @param useCapture If true, <code>useCapture</code> indicates that the user wishes to initiate
   * capture. After initiating capture, all events of the specified type will be dispatched to the
   * registered <code>EventListener</code> before being dispatched to any <code>EventTargets</code>
   * beneath them in the tree. Events which are bubbling upward through the tree will not trigger an
   * <code>EventListener</code> designated to use capture.
   */
  public void addEventListener(String type,
      EventListener listener,
      boolean useCapture);

  /**
   * This method allows the removal of event listeners from the event
   * target. If an <code>EventListener</code> is removed from an
   * <code>EventTarget</code> while it is processing an event, it will not
   * be triggered by the current actions. <code>EventListener</code>s can
   * never be invoked after being removed.
   * <br>Calling <code>removeEventListener</code> with arguments which do
   * not identify any currently registered <code>EventListener</code> on
   * the <code>EventTarget</code> has no effect.
   *
   * @param type Specifies the event type of the <code>EventListener</code> being removed.
   * @param listener The <code>EventListener</code> parameter indicates the <code>EventListener
   * </code> to be removed.
   * @param useCapture Specifies whether the <code>EventListener</code> being removed was registered
   * as a capturing listener or not. If a listener was registered twice, one with capture and one
   * without, each must be removed separately. Removal of a capturing listener does not affect a
   * non-capturing version of the same listener, and vice versa.
   */
  public void removeEventListener(String type,
      EventListener listener,
      boolean useCapture);

  /**
   * This method allows the dispatch of events into the implementations
   * event model. Events dispatched in this manner will have the same
   * capturing and bubbling behavior as events dispatched directly by the
   * implementation. The target of the event is the
   * <code> EventTarget</code> on which <code>dispatchEvent</code> is
   * called.
   *
   * @param evt Specifies the event type, behavior, and contextual information to be used in
   * processing the event.
   * @return The return value of <code>dispatchEvent</code> indicates whether any of the listeners
   * which handled the event called <code>preventDefault</code>. If <code>preventDefault</code> was
   * called the value is false, else the value is true.
   * @throws EventException UNSPECIFIED_EVENT_TYPE_ERR: Raised if the <code>Event</code>'s type was
   * not specified by initializing the event before <code>dispatchEvent</code> was called.
   * Specification of the <code>Event</code>'s type as <code>null</code> or an empty string will
   * also trigger this exception.
   */
  public boolean dispatchEvent(Event evt)
      throws EventException;

}
